The use of chain guides is known in the art. A chain guide is also known as a stationary arm, which is stationary in relation to a moving endless chain, thereby guiding the chain along a desired path and preventing unwanted side-to-side motions. Typically, a chain guide works in conjunction with a chain tensioner that takes up excess slack to keep the endless chain in a desired tensioned state.
U.S. Pat. No. 6,447,414, which is hereby incorporated herein by reference teaches a chain tensioner system having a hydraulic tensioner and a tensioner arm with a spring blade. A hydraulic tensioner applies force against the end of the tensioner arm. The arm is pivotally supported at one end and supported by the tensioner piston at the other end. A blade spring is inserted into the plastic shoe to provide tension to the arm.
Typically a chain guide is positioned opposite the tensioner system in that one strand, or portion, of the endless chain is in contact with the chain guide and another strand of the same endless chain is in contact with a shoe or face of the chain tensioner. Over the operating life time of a chain system such as an engine timing chain system, the characteristic of the chain system tends to alter. In other words, for a chain system, it is important to impart and maintain a certain degree of tension to the chain to prevent noises or slippage. Prevention of slippage is especially important in the case of a chain driven camshaft in an internal combustion engine because slippage may alter the camshaft timing by several degrees, possibly causing poor performance or even damage to an engine system. In the harsh environment in which an internal combustion engine operates, chain tension can vary between excessively high or low levels as a result of the wide variations in temperature and differences between the coefficients of linear expansion among the various parts of the engine, including the chain and the tensioner system that keeps the chain in a suitable tension. Furthermore, camshaft and crankshaft induced torsional vibrations cause chain tension to vary considerably. This tension variation results in chain elongation. Moreover, wear of the chain components during prolonged use can cause permanent elongation of the chain that results in a decrease in the tension of the chain. To keep the chain in the suitable tensioning state, a tensioner arm is required in many cases.
Therefore, it is known to use an elastic element such as the blade spring of U.S. Pat. No. 6,447,414 to, in part, maintain the requisite tension of the chain. However, chain guides are usually designed to be rigid or stationary. Blade springs are not known to be used or incorporated in a chain guide system. Compliance in the guide can improve drive behavior by reducing impact forces on the wear surface, and also can reduce forces on the supporting brackets and/or guide mounts. Therefore, it might be desirous to have a suitable device incorporating an elastic member such as a blade spring in a chain guide to provide some elasticity or compliance. The distinction between the compliant guide and the rigid or flexible tensioner arm is that the guide is only designed to provide a small amount of compliance in order to reduce forces, whereas the tensioner arm is designed for a much larger range of motion in order to accomodate chain wear and stretch.